#! perl -slw use strict; our $N //= 10e6; my %hash; my $val = 'AAAAA'; undef $hash{ $val++ } for 1 .. $N; my $start = time; open SORT, '| sort > sorted' or die $!; print SORT $_ while $_ = each %hash; close SORT; undef %hash; open IN, '<', 'sorted' or die $!; chomp(), $hash{ $_ } = $. while ; close IN; my $elapsed = time - $start; printf "Took %.6f seconds for $N items (%.5f per second)\n", $elapsed, $elapsed / $N; __END__ C:\test>junk41 -N=10e6 Took 225.000000 seconds for 10e6 items (0.00002 per second)